This application is related in subject matter to co-pending application no. (Attorney Docket No. 051481-5102), entitled xe2x80x9cPurge Valve With Integral Diagnostic Member,xe2x80x9d filed on the even date.
The present invention relates to a vapor purge system, and more particularly to a purge system including a valve that provides a reliable measure of flow through the valve.
In a system that is known to Applicants, a valve is used to deliver fuel vapor to an engine intake manifold for use in a combustion process.
In the known system, a fuel tank is in fluid communication with a charcoal canister, such that the charcoal canister receives vaporized fuel from the tank. The collected vapor is delivered from the canister through a delivery port. The valve includes an input and an output, the input being in fluid communication with the delivery port.
The diagnosis and evaluation of flow through the known system is achieved between the delivery port and the inlet port of the valve. In particular, a t-fitting is disposed between the delivery port and the valve. Thus, a direct flow path between the delivery port and the valve is split by the t-fitting, the direct flow path replaced by three flow paths, in particular (1) a flow path from the delivery port to a first arm of the t-fitting, (2) a flow path from the second arm that permits evaluation of the system, and (3) a flow path from the third arm of the t-fitting to the valve for delivery. Diagnosis and testing of the flow diverted through the second arm of the t-fitting is accomplished through a testing member. The flow paths are fuel grade hoses.
A fourth flow path, also in the form of a fuel grade hose, is used to deliver fuel vapor from the valve (i.e., from the valve output) to the engine intake manifold for combustion.
Thus, from the delivery port to the valve output of the known system, four hoses and seven connections are required. The seven connections are as follows: (1) at the vapor delivery port, (2) at the first arm of the t-fitting, (3) at the second arm of the t-fitting, (4) at the third arm of the t-fitting, (5) at the testing member, (6) at the inlet port of the valve, and (7) at the outlet port of the valve.
Multiple separate brackets are used to mount the valve and the testing member with the motor vehicle chassis.
The known system suffers from a number of disadvantages, in that each hose, connection, and additional, separate component (e.g., the t-fitting) increases the cost and the complexity of the system. Further, each additional connection provides an additional potential leak point within the system. Because vapor can leak from the system between the flow evaluation point and the valve, testing to determine flow through the valve becomes less accurate as the number of leak points increases between the evaluation point and the valve. A multiplicity of brackets for mounting of the valve and the testing member also increases the complexity and the cost of assembly of the known system.
The present invention provides a vapor purge system that permits evaluation of the system with a minimum number of hoses and connections, and without the use of additional components. The system includes a valve having first and second ports in communication with a first chamber and a third port in communication with a second chamber, the first and second chambers being defined by a metering member that divides an internal volume of a housing. A first conduit connects a diagnostic member having first and second operative states with the first chamber, the connection being made through the second port. The first operative state prohibits communication with an exterior of the valve, and the second operative state permits communication with the exterior. The diagnostic member provides the ability to reliably measure flow through the valve. The system can use three (3) hoses including five (5) connections from a vapor supply port connected with the first port to the third port operatively connected with a manifold.
The present invention also provides an evaluation assembly. A valve includes a housing defining an internal volume. A metering member is disposed in the housing, the metering member dividing the internal volume into first and second chambers. A first port is in communication with the first chamber. A second port is in communication with the first chamber. A third port is in communication with the second chamber. A first conduit provides a flow path from the second port to a diagnostic member. The diagnostic member provides the ability to reliably measure flow through the valve.
The present invention also provides a method of evaluating a vapor purge system having a vapor collection arrangement, a valve, and a diagnostic member. The valve includes a housing defining an internal volume, a metering member disposed in the housing to divide the volume into first and second chambers, a first port in communication with the first chamber, a second port in communication with the first chamber, and a third port in communication with the second chamber. The diagnostic member is in communication with the second port, the diagnostic member having a first operative state that prohibits communication with an exterior of the valve and a second operative state that permits communication with the exterior. A conduit provides a flow path from the second port to the diagnostic member. The method includes locating the diagnostic member above a top-most surface of the valve, sealing the first chamber from the second chamber with the metering member, and measuring a flow through the first chamber of the valve.